On the domestic front, Gore isn't going to get much done with the Republicans still in control of Congress. I don't think 9/11 is going to increase the Democrats' numbers, either, so that means an even larger Republican majority. I would assume that the only big thing Gore gets done on the domestic front is persuading the GOP to work with him on energy independence.
On the foreign policy front, I think that Gore would be more cautious than was President Bush. The response to 9/11 would be more or less the same, with someone like Colin Powell heading up Defense, but with a larger focus on getting Bin Laden instead of say, an invasion of Iraq. If Gore catches Bin Laden and creates taskforces to deal with international terrorism, he'll have responded better than Bush. I don't see him trying any sort of intervention in Iraq, quite frankly, because it wouldn't make sense.